Federally sponsored research and development:
Not Applicable.
1) Field of the Invention
This invention relates to a stringing for a sports racket such as, but not limited to, a tennis racket or a racket-ball racket.
2) Background Information
Conventional tennis rackets are strung with strings passed above and below each other to produce a woven string network. Since the strings are not bonded at their crossover points, the pattern of the string network may deform when the ball is struck by a racket with an upwards or downwards component of motion, such as that used by players wishing to place a spin on the ball. The movement of the strings relative to one another produces wear through attrition and leads to premature string failure. This effect is accentuated when the tennis game is played on clay, where clay micro particles are brought to the racket by the tennis ball and, upon reaching the location of string attrition, accelerate the process of wear.
U.S. Pat. No. 4,741,531 by Szedressy and U.S. Pat. No. 4,949,968 by Korte-Jungermann permit replacing a single broken string without rebuilding the entire string network. These designs share the basic idea of building the string network with individual string segments that traverse the string network only once and are attached to the racket frame at oppositely disposed locations via a fixing means. In both cases, extra tension must be applied in the process of stringing the racket in order to compensate for a string shortening caused by a yield of the fixing means in the string axial direction following the release of the string by the string tensioning means. The axial yield alters the string tension and complicates the stringing process.
As will be seen from the subsequent description of the preferred embodiment of the present invention, these and other shortcomings of the prior art are overcome.
The preferred embodiment of the present invention has a new string design wherein strings interlock with one another at the string crossings. The interlocking is achieved through matching surface indentations on the strings at the location of the string crossings, the matching surface indentations allowing lateral forces to be transmitted between the crossing strings.
The interlocking strings are woven in the usual interlaced pattern and placed under axial tension, wherein the combination of tension and the matching surface indentations allows the crossing strings to transmit both lateral forces and bending moments to one another, thus maintaining the strings in their relative position and orientation during, and after, the transient motion of the string network resulting from the impact between the string network and a sports ball. Consequently, strings with aerodynamic cross-sectional area can maintain the correct orientation of least aerodynamic drag.
The string attachment to the frame is accomplished by a fixing means wherein the desired radial string compression is produced via a wedging action between a string clamping member and a pressing means, with the string clamping member being also prevented from moving in the string axial direction.